1. Technical Field
The invention is related to a microphone array preamplifier measurement system, and in particular, to a system and method for automatically determining gain variations between one or more analog microphone/preamplifier channels in a microphone array and a system and method for automatically compensating for such gain variations to provide for improved processing of audio signals captured via the microphone array.
2. Related Art
Conventional microphone array type devices are well known to those skilled in the art. In general, microphone arrays typically include an arrangement of microphones in some predetermined layout. These microphones are generally used to capture sounds from various directions and originating from different points of the space. Once captured, onboard sound processing software and hardware then provides sound processing capabilities, such as, for example, sound source localization, beam forming, acoustic echo cancellation, noise suppression, etc.
For example, one common use for such arrays involving audio conferencing systems is to determine the direction of a dominant speaker in a room having both active speech and other noise, and then to process the input from the various microphones in the array accordingly. In particular, given the input from each of the microphones in the array, conventional beam forming and sound source localization computations are used to localize the position and direction of the person currently speaking. With this information, it is then possible to filter out all sounds not coming from the direction of the speaker, thereby improving the overall quality of the captured sound with respect to the person speaking.
In general, such microphone arrays typically include one or more sets of matched microphone/preamplifier combinations. In other words, the electronic components, i.e., microphones, preamplifier circuits, etc., within such microphone arrays are carefully chosen so that that the frequency responses of the various microphone/preamplifier combinations within the microphone array are as close as possible to one another for any particular audio input. Matching the gains and frequency responses among the preamplifier circuits is important because variations across channels degrade the performance of the aforementioned beam forming and sound source localization algorithms.
Unfortunately, choosing electronic components for matching the frequency response of the various microphone/preamplifier combinations within a microphone array is typically rather expensive, thereby increasing the cost of such microphone arrays. For example, choosing electronic components with matching responses is typically accomplished either through the careful testing of a large batch of individual electronic components to identify those with matching properties, or through the use of relatively expensive high-precision electronic components (capacitors, resistors, op amps, etc.) that are guaranteed to have particular electrical properties within some small tolerance. Both cases tend to significantly increase the cost of matched sets of microphone/preamplifier combinations for a microphone array.
Further, in the case where inexpensive electronic components of some nominal tolerance are used there will likely be a relatively wide variation in the frequency response of each microphone/preamplifier combination within the microphone array. As a result, in order to achieve optimal audio processing performance, the response of each individual microphone/preamplifier combination within the microphone array must be pre-determined, and any software designed to process audio signals captured by the microphone array must then be specifically tailored to the specific operational parameters of each microphone/preamplifier combination within that array. Consequently, each such microphone array typically requires customized software, thereby increasing both test time and cost to manufacture individual microphone arrays.
Further, the operational parameters of individual electronic components in a microphone array tend to change, if even only slightly, over time, and relative to the local temperature of such electronic components. Therefore, software tailored to a particular microphone array configuration may still produce sub-optimal audio processing results where the parameters of the microphone array fail to precisely match the expected operational parameters coded into any associated audio processing software or hardware.
Therefore, what is needed is a system and method for allowing a microphone array to avoid the use of expensive matched electronic components by allowing for the use of relatively less expensive non-matched electronic components. Further, rather than requiring software to be specifically pre-tailored to the particular operational parameters of each microphone/preamplifier combination within the array, the microphone array should instead be operable with software that automatically configures itself to the operational parameters of the microphone array. Consequently, such a system and method should automatically determine and compensate for variations in the gain and frequency response of each microphone/preamplifier combination within the array to allow for automatic configuration and optimization of audio processing software associated with the microphone array.